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BCSC > Psychophysics > Flashcards

Psychophysics Flashcards

1
Q

What is psychophysics

A

Quantitative branch of the study of perception

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2
Q

What does psychophysics examine

A

The relations between observed stimuli and responses, as well as the reasons for those relations

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3
Q

Who founded psychophysics

A

Gustav Fechner

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4
Q

When was psychophysics founded

A

October 22, 1850

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5
Q

What was Gustav Fechner seeking to do when founding psychophysics

A

Wanted to calibrate the mind relative to physical stimuli

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6
Q

What is the first requirement in a psychophysics experiment

A

Human/nonhuman subjects are tested in an expirimental environment that maximizes control of stimulus variations over variations in the subjects responses

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7
Q

What is the second requirement of psychophysics experiments

A

Stimuli carefully controlled, often varying along only a single physical dimension (ex: intensity)

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8
Q

What is the third requirement for psychophysics experiments

A

Subject’s responses are highly contrained (ex: “yes, i see stimulus” or “no i dont see stimulus”)

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9
Q

What is the fourth requirement of psychophysics experiments

A

Small numbers of subjects are tested with extensive within-subject designs

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10
Q

What do psychometric functions typically look like

A

Sigmoid “S” shape with the x variable being invisible near zero and visible near 100, and the y variable being percent that said “yes”

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11
Q

What are the three types of measurements in a psychophysics experiment

A

Absolute threshold
Difference threshold
Point of subjective equality (PSE)

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12
Q

What is the absolute threshold

A

Lower limit of perception; weakest stimulus that can just barely be detected

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13
Q

What is the difference threshold

A

Smallest reliably discriminable difference between two stimuli

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14
Q

What is difference threshold also known as

A

JND (just noticeable difference)

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15
Q

What is the point of subjective equality (PSE)

A

Magnitude of one stimulus at which it is perceived as equivalent in magnitude to another

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16
Q

What percentage of people are able to notice the PSE

A

50

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17
Q

What percentage of people are able to notice the JND

A

75

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18
Q

What is the x axis gap between the PSE and JND known as

A

IND

19
Q

What are the two techniques for measuring thresholds and PSEs

A

Yes-No Tasks
X AFC Tasks

20
Q

What are Yes-No Tasks

A

NO option is the absence of something; typically used in detection tasks

21
Q

Are Yes-No Tasks subject to bias?

A

Yes. Bias is corrected by the SDT

22
Q

What happens in Yes-No Tasks when the participant is unsure

A

Answer is guided by personal biases

23
Q

How is the threshold determined in Yes-No Tasks

A

Threshold set to 50%

24
Q

What are X AFC Tasks

A

A choice between multiple, corresponding alternatives; used in discrimination tasks

25
Q

Are X AFC Tasks subject to bias

A

No

26
Q

What happens when subjects in X AFC Tasks are unsure

A

They’re forced to guess

27
Q

What is the “pure” guessing performance determined by in X AFC (with example)

A

X (example, for 2 AFC = 50%, 4 AFC =25%)

28
Q

What does the guessing range determine

A

The lower performance limit

29
Q

What is the threshold set to in X AFC tasks

A

Set to halfway between the guessing rate and 100%

30
Q

What are the three procedures for measuring thresholds and PSEs

A

Method of adjustment/limits
Method of constant stimuli
Staircase method

31
Q

What is the method of adjustment/limits

A

Person adjusts stimulus to value where it is barely detectable (absolute threshold) or adjusts one stimulus until it matches another (PSE) or differs from another (JND)

32
Q

What is the difference between the method of adjustment and the method of limits

A

Adjustment: Stimulus adjusted by subject
Limits: Stimulus is manipulated by the experimenter or a computer program

33
Q

How are the results of the method of adjustment/limits measured

A

Lower/raise until just barely detectable
Repeat X number of times
Average the values to estimate the threshold

34
Q

What is the method of constant stimuli

A

Present stimuli at various levels; person responds (ex: yes or no) following each presentation, generating a psychometric function

35
Q

Describe method of constant stimuli in depth

A

Display stimuli in random order and repeat many times
For each trial, subject indicates their perception of the stimuli
Plot subjects’ answers as response probablility vs stimulus value
Estimate the threshold and/or slope

36
Q

How many times should the constant stimuli method be repeated per stimulus level

A

~40

37
Q

What is the staircase method

A

Adaptive search for threshold

38
Q

What does a subject’s response (correct/incorrect) determine in the staircase method

A

Correct -> following trial is harder
Incorrect -> following trial is easier

39
Q

What are the two types of staircase method

A

Fixed step size
Adaptive step size (asking where somebody is from analogy)

40
Q

What is the staircase method designed to do

A

Converge to a certain threshold value

41
Q

What are the pros of the constant stimuli method

A

Gold standard of psychophysics
Yields a complete psychometric function

42
Q

What are the cons of the constant stimuli method

A

Takes many trials
Requires pre-selecting stimulus levels

43
Q

What are the pros of the staircase method

A

Fastest method for estimating threshold
Doesnt require pre-selecting stimulus levels, just the starting point
Great for non-expert subjects

44
Q

What are the cons of the staircase method

A

Does not yield a complete psychometric function
Focuses on estimating the threshold

BCSC (7 decks)

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